Abstract
The critical behavior of the manganese La
0.75
Ca
0.25−x
Na
x
MnO
3
(
x
= 0.00; 0.05) was studied around the PM-FM phase transition. Various techniques are used to obtain the critical exponents of our samples; such as modified Arrott plot (MAP), Kouvel–Fisher (KF) method and the critical isotherm analysis (CI) around the Curie temperature (Tc). The experimental results indicated that our samples had a second-order magnetic phase transition. Based on the above methods, the critical exponents (
β
,
γ
and
δ
) were extracted in the low- and the high-magnetic fields from the magnetic isotherms data. The obtained critical exponents were close to those expected for the Tricritical Mean-Field model. These critical exponents obey to the Widom scaling relation
δ
= 1 +
γ
/
β
, which proves the reliability and the self-consistency of all critical exponents values. The magnetization–field–temperature (
M
–
µ
0
H
–
T
) falls into two curves, below and above T
C
. It follows the single scaling equation
M
H
,
ε
=
ε
β
f
±
H
ε
β
+
γ
with
ε
= (
T
–
T
C
)/T
C
is the reduced temperature. This confirms the reasonability of the critical exponents with the scaling hypothesis. Moreover, the analysis of the effective exponents
β
eff
and
γ
eff
indicates that
β
eff
(
ɛ
) for the two samples and
γ
eff
(
ɛ
) for
x
= 0.00 are self-consistency and in good agreements with the Tricritical mean-Field model, but
γ
eff
(
ɛ
) for
x
= 0.05 is heterogeneous with any class of predicted universality.